“For 2018, we intend to grow this profitable segment of our business,” Centene CEO Michael Neidorff said on a call with investors last month.

The only potential region without an ACA offering in 2018 is a rural western Ohio county where just 334 people enrolled this year. Jillian Froment, director of the Ohio Department of Insurance, told Politico that she is “hopeful” she can still attract a company to Paulding County.

While insurers like Centene are being applauded for stepping up to the plate, “that doesn’t mean everything is hunky-dory,” Jonathan Cohn writes in for the Huffington Post.

“Centene’s business model relies on narrow physician networks to keep premiums down, which isn’t what all consumers would prefer,” Cohn writes. “And although the number of truly bare counties has now shrunk to nearly zero, there are still many that only have one insurer.”

While roughly 40 percent of all counties will have just one exchange insurer in 2018, those counties are disproportionately rural, with few people living in them, he writes. Even before the ACA was enacted, insurers typically found rural counties “inherently difficult” to manage because of the less-than-ideal healthy-sick ratios, and “because the relative paucity of doctors, hospitals and clinics makes it impossible for insurers to play providers off of one another to get lower prices.”

Cohn listed several ways policymakers could mitigate this risk, including creating new “reinsurance” programs, which subsidize the consumers with the most serious medical problems — something that Alaska and Minnesota have already done. Other options include expansions of Medicaid, Medicare or the federal employee health plan.

“Some of these ideas would do more that merely stabilize markets,” he writes. “They would make health care more affordable for the millions who still can’t pay for it easily, a problem that even most Obamacare defenders concede the law did not fully solve.”